How Does a Piano Work? (Inner Mechanisms Explained)

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When you press a key on a grand piano it causes a hammer to strike tuned strings and lift a damper. The strings vibrate which makes a noise that is then amplified by the soundboard. Releasing the key drops the damper and dampens the noise.

Inside of a grand piano

The grand piano is a complex instrument with many moving parts. Now that you know the basics of how it works, let’s dive into a more in-depth explanation of how the keys, hammers, strings, and pedals interact to make music.

What are the 4 main parts of a piano?

While there are many parts in a grand piano that are important to its design, there are four main parts. They are the keys, hammers, strings, and pedals. Each one serves a distinct purpose in generating the sounds that become music.


Piano Keys

A grand piano has 88 keys that are divided into 52 long white keys and 36 shorter black keys. Each key corresponds to a different note with the white keys covering natural notes and the black keys covering sharp and flat notes.

The keys are most commonly made of wood, usually spruce for the white keys and ebony for the black. Keys are also commonly covered in plastic to improve their durability. White keys used to be covered in ivory before 1975 when the Asian elephant was classified as endangered.


Piano hammers

There are 88 hammers that correspond with the 88 keys of a grand piano. The hammers are also made out of wood except for the part that strikes the strings. The head of the hammer is made of felt.

This felt head is applied to the hammer using a special device. This makes the felt head very dense and compressed.


Piano strings

You might be surprised to learn that the number of strings is not the same as the number of keys and hammers. Most grand pianos have 230 strings though it can vary depending on the manufacturer.

The low bass notes have thicker strings and only one per key. As the pitch of the note increases, so does the number of strings. Treble and tenor notes have three thinner strings per key. The difference in string numbers between manufacturers comes from that transition.


Piano pedals

Beneath a piano, there are three pedals that affect the sound in different ways. From left to right they are the shift or una corda, sostenuto, and sustain pedals. They each have different names in addition to these.

The shift pedal, as the name implies, shifts everything from the keys to the hammers slightly to the right. This makes the hammer strike only two of the three strings. In the case of notes with only one string, the hammer strikes with a less used part of the felt head. 

This pedal works differently in an upright piano. Instead of shifting the hammer to one side, it moves them closer to the strings. This softens the noise made but does not affect the tone.

The sostenuto pedal is an interesting one. This one allows you to lift the damper from individual notes even after the corresponding key has been released. Only the keys that were depressed when you use this pedal are affected.

The far right pedal is called the sustain pedal because it removes the damper from all of the strings. It is a less specific sostenuto pedal. The sustain pedal allows all notes played to continue after their key has been released.

Other important parts of a piano

While there are other parts beyond the above four they aren’t as essential to understanding how a piano works. Nonetheless, they are good to know. Other important parts include the soundboard, action, tuning pins, hitch pins, bridge, agraffe/bearing.

Of these, the most important is the soundboard. If you were to have a piano without one, it would be very quiet. The soundboard vibrates with the strings because of the bridge that supports them. This extra vibration amplifies the sound. It is often called the soul of the piano.

How do the 4 main parts of a piano interact?

Now let’s get into the meat of it. How do these different parts cooperate to make the beautiful sounds you associate with a piano? It all starts with the pianist of course. The pianist presses on a key.

When a key is depressed, the end of it that is inside the piano lifts. It then hits a part called the action. The action takes that motion and uses it to throw the hammer up at the string or strings depending on the note.

The hammer strikes the strings with the same force that the pianist pushed the key. The harder the key is pressed, the faster the hammer strikes. This affects the volume of the note.

Once struck, the strings begin to vibrate. The length, thickness, and tension all determine what the note sounds like. Different strings vibrate at different frequencies. For example, a string properly tuned to the note A will vibrate at 440 hertz.

The vibrating string will produce noise, but as mentioned above it will be rather quiet. This is solved by the soundboard. 

The strings are supported by a piece of wood called the bridge on the end of a grand piano farthest from the pianist. The vibrations from the string travel into the bridge and from there into a wooden soundboard. The soundboard vibrates along with the strings and increases the sound produced.

So that is how pianos make sound, but what about the pedals? These are for the pianist to have more control over the sound of the piano. 

Normally, the damper, a series of wood pieces with felt pads, is controlled by the keys. When a key is pressed, the damper lifts from the corresponding strings to allow them to vibrate. When the key is released, the damper falls back onto the strings.

The middle and the right pedal both change how the damper works as described in the pedal section. The left pedal changes the hammer interaction as mentioned above.

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